Boronized conductor and method of manufacture.



' iSTATES, PATENT OFFICE. 7

wnm'raauni-or nrunjnassacnusn'rrs, assrenon' 'ro GENERAL anaemic compan aconrom'rxou or new Yom 5 lamp, a furn:uce,v-orathe like,and likewise for other purposes in the electrical art, for example, as a materialfi for making brushes.

.My1n-esent application isdirccted to the action of boron on 'carbon, and to the product resulting fromthatfaction which I have hereinafter designated boronized carbon. As a specific embodiment of the basic idea of my present invention, I will describe the treatment with boron of what is known among lamp makersas a-base filament.

. If a basefilament of small cross section is heated .with current to bright red heat in a mixture of boronchlorid and hydrogen, a

deposit of boron is obtained on-the filament so as disclosed and claimed in my application,

Serial No. 585,390, filed October 5, 1910.

-- .-The deposition of a very-little boronis 5 iiicientfor my present purpose; Ifnow he 1 coatedfilament-be embedded in carbon or. -35.graphite, packed in a crncible, and then heated to about 2,000-dcgrees centigrade for some time, either n a vacuum furnace of the type shown in the United-States Patent to- Arsem, No. 785,535 of March 21,1905, or in 40' an ordinary electric ff u'rnace, 'the filament will be found, on removal from theffulfnace',

A to have 'ehanged in resistance, and further- .more' to: .haveacquired; a marked 'jpositive temperature coeflicient; Neitherv the original base filamen'ts nor. 'ure boroIi-has a. positive tempirature coe ci ent. ".The' filament" ,can-also heated by-the directpassageof 1 current through the same.- During the firing most of the-boron vaporizes, though it is pos-.

sible that mere-traces may remain,-and by some peculiar actionon the carbon of the.

- base filament, convert it intofithat form of carbon possessed of a low ohmic reslstance and a positive tom 5- designated in the c aims as boronized. car- Specification of Letters Patent. s asm sled October a, 1909. seriaiuo; 52mm] rature coeflicient' and "aoaon'xiznn comuc'roa nnn mnrnon oF---mnrac'rma.-

Patented Ma. 5, 1912 hon. The filament resulting from this operation may be mountedin ajamp and used under commercial"conditions as alight giving source, or itmay be-used as a fillet or core on which to deposit additional material for building up a conductor of large cross section.

As another embodiment of the basic invention herein set forth, I will describe an operation in which the boron is used to roduce changes in carbon deposited on a llet from a volatile carbonauous compound.

Starting with a base filament either of above described, I de osit unit a very thin coatiugof boron. This may be done by heating the filament with current in the abovement-ioued mixture of'hydrogen and boron chlorid. I next' ,remove the filament to a chamber containing gasolene or other suitable carbona'ceous vaporlaud there deposit a layer'of carbon in well-lmown manner. The filament then consistsrof a core enveloped in a boron layer, and with an outer coating of 'carbon. The amount of boron is small and only a part of one..percent of the amount of carbon. The next operation consists in heating this composite filament either with current, or-in a suitable furnace to cause action of th boron on the carbon coating. This action may be called ,boronization and the car- 'bon so acted on may becall'ed boronized car- 'bon. .As a result of the heat treatment, the

tive to,-'positive, tbe surface of the filament becomes grayand metallic and is so constituted that its vapor tension is far below that of either carbon or boron. A filament so treated or boronizedcan'be operated in an incandescent lamp at high temperature without detrimental blackening of the bulb.

As athird. and preferred embodiment of the basic'idea-otmy present invention, I will -'des'cri be the production of a stable the presence of boron, and under such con- ,ditions. that the boron exerts its converting power and changes the carbon,deposit from ordinary carbon to what may be designated vapor tension, low specificresistance, and a This result may be attained by heating a temperature .coefiicient changes from negalamp filament by deposition of carbon in positive temperature co'eflicient of resistance.-

.base filament, either of the borouized type or otherw se, in a mixture of boron chlorld I ordinary type,- or after" boronization, as

as boroniz'ed carbon characterized by low I and gasolene, or carbon tetrachlorul, or other carbon-containing vapor. For if the filamentlic heated with current, as inthe ordinary treating operation, carbon will be deposited from the gasolene, and the presence of boron chlorid in the treating cham her will insure -conversion of the deposited carbon into carbon of the desired typei. Careful tests for boron show that only traces exist inthc final product.

I have investigated the relative proportious of gasolene and boron chlorid best suited for this work, and have obtained bestresults with a mixture consisting of gasolene at a pressure of three millimeters of mercury tobor'on chlorid at a pressure of 24 millimeters ofmercury. As an alternative treating mixture for the carbon deposit-ion above described, I may-use 100 millimeters of hydrogen, 24'millimeters boron chlorid, and 24 carbon tetrachlorid; The

conditions are alwaysjso chosenas to give a Small P centa e of'boron in the 'deposited-carbon.-- Y

' In the specific embodiment above set forth,

boron chloridyhas been relied 'on as' the closed.

' As'one special advantage of the use of 'lialid' which undergoes decomposition,- but other h'ahds maybe used since theytoo'will yield a suitable deposit when handled according to the steps of the process here disboron, mention maybe made of the low temperature at which the boron brings about- 35 Although this temperature varies somewhat the remarkable changes in the carbon.-

in. accordance, with. the particular variety of carbon winder treatment, nevertheless,

with gasolene carbon produced, when boron chlor1d and gasolene are used as the. treat- ,a ing mixture, the temperature of boroniza-;

tion may be well below 2,000 degrees (3;, and.

even-in some cases as low as 1,000 degrees C. I have descr bed my invention as applied to theproduction of incandescent lam filaments, but Irecognizethat it. is app 1cableto the treatmentlot conductors of larger size, such, for instance, as electrodes and especially brushes;

As to the theory of the .action of 'the boron, I am inclined to consider the "resulting'product as-a solid solution of a very small quantity of boron in carbon. It is remarkable that "a substance like boron with by Letters Patent ofthe United States. is,-

fying the character-of said-deposited carbon thr'oughthe action thereon. of boron. 4, The method ofconstructing a conductor having a positive temperature'coetlicient,

which consists in .de ositlng carbon-foil a heated, conductive b y and 'governing "the character of the 'depos'itbytheaction of a boron'halid." y r 5. The method-lot constructing aeonductor which consistsin' depositing carbon of low vapor tension, low-specific, resistance and positive temperature coe'fiicient,byheating a'conductive bodytin a mixture of boron halid and a volatile hydrocarbon.

6. The method of 'treatlingjalainp fila-- ment, which consists in heating thefilamcnt with electric current in a mixture of boron chlorid and-gasolene. Q

' .7. Aconductor ofjcarbonfasjsociated; with a very small quantity of boron and characterized by a positive temperature coefficient and "a specific 'resistan'ce'lower than "that of carbon asdepositedifroln gasolene. a

8. A lamp filament consisting- OfzliijCOll: ductive cor'e enveloped in carbon associated with a very little. boron and having aposi- '9.- A lamp filament consistingjofi a-Lcore enveloped in a solid solution of boron in carbon and characterized a positive-telnperature coefficient. anda specific resistance "lower than that of carbon depositedjrom gasolene, v

- 10.- Themethod of treating a;-fil ament,

material deposited. on the filament shall consist in large part of carbon with aipositive temperature coeflicienh i I a In witnesswhereof -l have-hereunto set my -hand this 26th day of October, 1909.

v .EZECHIEDWEINTRAUB. Witnesses' Jomt AtMoMamis, Jr. CHARLES A; Bamako.

whichconsists in heating fit'jwith electric current in a gaseous mixture contain ng 'bor'o'n chlorid andgasolene, these materials being mixed in' such proportions that the 

